In percussive drilling, energy is transmitted from a rock drill through a drill steel and the drill bit to the rock where the energy is used to perform crushing work.
The rock drill is provided with a piston which is thrown forwards to strike the shank of the drill steel, the energy of the piston passing into the drill steel and through the drill bit in the form of an impact wave.
Conventional drill steels are formed of elongate steel rod, and are often provided with a central throughbore to carry flushing fluid, such as water, air or foam from the drilling rig to the bit to flush out the loosened rock chippings. Drill steels may be of a variety of sizes, typically being between 2 and 22 feet long. Smaller, less substantial drill steels or extensions between a driver and a bit are used in many other industries, notably in the construction industry.